Band-spread tuning mechanism



June 2, 1942. H. GUSDORF 5,

BAND-SPREAD TUNING MECHANISM Filed May 11, 1940 2 Sheets-Sheet 1 J a AINVEN TOR. FREDER/K HENDR/K GUSDORF A TTORNEY June 2, 1942. F. H.GQSDORF BAND-SPREAD TUNING MECHANISM Filed May 11, 1940 2 Sheets-Sheet 2T0 POINTER 0F BAND SPREAD TUNING SCALE I N VENTOR.

MM 0 @WW 0 6 m H A 0. 1 M mw spread tuning means Patented June 2, 1942uBAND-SPREAD TUNING MECHANISM Frederik Hendrik Gusdori', Eindhoven,Netherlands, assignor to Radio Corporation of America, New York, N. Y.

Application May 11, 1940, Serial No. 334,499

1 In Germany June 22, 1939 4 Claims.

In the copending application of Arnold T. Vossen, Ser.- No. 297,972,filed October 5, 1939,

there is described a device for obtaining bandspreading in short-wavereception. In one of the examples described therein the band-spreadtuning means are constituted by inductance coils included in theoscillatory circuits to be tuned and in the field of which membersseated on a shaft can be displaced by means of a screw thread drivingthe shaft.

The present invention relates to a radio receiver as describedin theabove application in which band-spread tuning means are displaced by atransmitting mechanism which also displaces the pointer of theband-spread scale.

The invention has for its object to enable preliminary adjustment of theband-spread means in two positions.

In the manufacture of a number of identical band-spread tuning means itis impossible from the economical point of view to equalize themcompletely.

It is Well known to make the band-spread tuning means variable so thatthe band-spread scale is correct at at least one point.

According to the invention the starting point and the length of the pathwhich the banddisplacement of the dependently of each other.

When the band-spread tuning means are constituted by elements mounted onas'haft and displaced in the field of inductance coils associated withthe oscillatory circuits to be tuned the shaft can be adjusted in thedirection of its length according to a suitable embodiment of theinvention.

In this case the shaft is-preferably driven by the intermediary of alever with which the ratio between the distances of the point of powerand the point of load from the point of rotation can be varied. 4 Inthis case the movement of the lever can be transmitted to the shaft bythe intermediary of a member provided with a set screw which is in linewith the shaft and bears on this shaft and with a. set screw which inone of the extreme positions of the member is parallel with the leverand which serves for the adjustment of the ratio between the distancesof the point of power and the point of load from thepoint of rotation.

In order that the invention may be clearly understood and readilycarried into effect it will now be described more fully with referenceto the accompanying drawings, in which Fig. 1 shows an oscillatorycircuitincluding a band-spread tuning element.

Fig. 2 is a graph of the variation of the inductance of such anoscillatory circuit as a function of the displacement of the band-spreadtun-' ing element.

Fig. 3 shows part of the transmitting mechanism between the tuning knobserving for bandspreading and the band-spread tuning means to be driven.

Fig. 4 shows the entire nism.

The oscillatory circuit shown in Fig. 1 includes a fixed inductance L1in series with a variable inductance L2. A tuning condenser C1 and atrimmer condenser C2 are connected in parallel therewith.

The tuning circuit can be tuned in the entire short short-wave range(for example from 13 meters to 50 meters) by means of the tuningcondenser C1. By means of the inductance L2 bandspread tuning can beeffected within a number of comparatively narrow short-wave bands. For

transmitting mechathis purpose tuning is first effected by means of C1to the center of the desired band,

the condenser after which tuning within the band concerned is effectedby means of the Variable inductance Lz.

traverse during a complete pointer can be adjusted in- The variation ininductance of the inductance coil L2 is several per cent of theinductance of the inductance coil L1. The trimmer condenser C2 permitsof correcting the tuning of the oscillatory circuit at a low value ofthe tuning condenser C1, for example 18 meters, and of altering the maintuning scale to accord at one point.

This must be efl'ected at a low value of C1 since in this case therelative variation of C2 is the great- I the main tuning scale is theinfluence of C2 at 43 meters is negligible. The main tuning scale can bemade correct at a second point, for example at 43"meters, by adjustingthe fixed inductance est. If, for example, correct at 18 meters of theoscillatory circuit. Since the inductance at 18 meters is the same asthe inductance 'at 43 meters a variation of the inductance at 43 metersexercises the same relative influence on the tuning at 18 meters. It isknown to bring about this variation in inductance b means of a smallvariable inductance coil in series with the fixed inductance. Theinvention permits however, of corrections of inductance being made bymeans of the band-spread tuning means.

Fig. 2 shows a system of coordinates XOY. the inductance of theoscillatory circuit being plotted as an ordinate and the displacement ofthe bandspread tuning means being plotted as an abscissa.

forced against the lever nism. Corresponding- Intermediate two plates zserves for the band-spread tuning. The adjustment of the starting valueL3 permits of the main scale being rendered correct at a second point.

Referring to Fig. 2, a and b designate two characteristics of theinductance as a function of the displacement of two band-spread tuningelements which are not entirely identical.

Since the two band-spread tuning elements have to exhibit the samestarting inductance L3 and the same final inductance the startingdisplacement of the band-spread tuning element having thecharacteristic. a is pa, where as the tuning displacement is qa. For theother bandspread tuning element these displacements are pi; and (11). Itis therefore necessary to arrange between the band-spread tuning knoband the band-spread tuning elements a transmitting mechanism by means ofwhich the displacements p and q can previously be adjusted for eachbandspread tuning element so that acomplete displacement of the pointerof the band-spread scale results in a variation in inductance from L1+Lt L1-l-L-l.-

Fig. 3 shows that part of the transmitting mechanism by means of whichthe two displacements p and q can be adjusted.

Thetransm itting mechanism comprises a part i adapted to slide on ashaft 2 which serves as a straight guide. The part i has mounted on it aset screw 3 which is in line with the shaft (shown at 39 in Fig. 4) thatcarries the bandspread tuning means. This shaft, which is not shown inFig. 3, engages the end surface 4 of the set screw 3. The part 1comprises in addition an angularly arranged set screw 5 which isprovided at the end with a disc 6. The disc 8 engages an upright edge 1of a lever 8 adapted to rotate on a shaft 9. The lever B is shown inFig. 3 in full lines in one of its extreme positions and in dotted linesin the other extreme position 8'. The lever B can be moved into any ofthe positions intermediate the said two extreme positions by means ofthe band-spread tuning knob and a screw, not shown in detail in Fig. 3.

When the lever 8. is moved into the position 8 the screw 5 is displacedtowards the position 5 shown in dotted Iinesbecause the part I is 8 by aspring (not shown) acting on the shaft of the band-spread tuning means.

On the screw 5 being screwed into the position lfl shown in dotted lineswhen the lever 8 occupies the position shown the part i is not displacedsince thescrew 5 isparallel with the lever B.

If, however, the lever B is'moved into the position 8 the screw 5 isdisplaced into the position l0 and thepart I traverses a correspondinglysmaller path.

The startingipoint p and the path q of the band-spread tuning means canbe adjusted by meansof the two; set screws 3 and Sand consequentlyindependently ofeach other.

. Fig ishows the entire transmitting mechaparts in' Figs-3 and daredesignatedby the.samc reference-numerals.

spaced apart by means of bolts 23 is arranged a shaft 24 which is partlythread 25.

l and 22 which are provided with screw face t by a spring (not shown).

The shaft 24 carries a rope drum 28. having wound in it the rope 21 of aflexible cable 28 which rope is connected with the pointer (not shown)of the band-spread tuning scale.

The rope drum 26 is coupled via a slipping coupling 23 to a gear wheel38 adapted to be driven by a gear wheel 31 mounted on the shaft 32 ofthe band-spread tuning knob (not shown). The slipping coupling protects25 from being damaged. On the shaft 24 being rotated a threaded strap 33is displaced over the shaft and along a straight guide 34 and thusdrives the lever 8. The lever B is adapted to rotate on a shaft 9 and issecured to the plate 2| by a strap 35. The lever comprises two parts 3and 36 connected by a rod 31. The movement of the strap 33 istransmitted to the lever 8 via the rod 31.

The movement of the the part I in the manner described with reference toFig. 3. I

The part i is displaced not only on the shaft 2 but also along astraight guide 38.

The end surface 4 of the screw 3 is engaged by a shaft 39 which isadapted to slide in a sleeve 40 and which is centered and guided by aplate,

H. The shaft .39 is forced against the endsur-f The shaft 39. carries aniron core 42 which is displaced, upon the shaft 39 being displaced inthe field of coil 43 wound around the sleeve 30 so that the in-'ductance of this coil is varied. The coil 43,

(which corresponds to the coil L2 in Fig. 1) forms part of theoscillatory circuit to be tuned.

When it is desired to tune more than one oscillatory circuit a pluralityof iron cores may be arranged on the shaft 38. The place of the shaft 39depends on the position of the end surface I of the screw 3.

The rotation of, this screw-3 permits of adjusting the starting positionof the shaft 39 and the final position of the shaft 39 can be adjustedby rotation of the screw 5 in the position shown of the lever 8. Thelatter adjustment is effected at a maximum induct-' ance of the coil 43.

What I claim is:

1. In a radio receiver of the type provided with one or morepermeability tuned circuits and wherein the tuning means for each suchcircuit is constituted by a magnetic core mounted on a shaft anddisplaceable in the field of an inductance coil included in the tunedcircuit, means for actuating said shaft in the direction of its length;said means comprising a carrierlmovable in'the direction of the shaft,settable means carried by said carrier for determining the initialadjustment of said shaft, additional settable means carried by saidcarrier fordetermining the extent of "linear displacement of the shaft,means for actuating the carrier through said additional means, andmanually operable means ance coilincluded in the tuned circuit; meansfor actuating said shaft inthe direction of its length, saidmeanscomprising a carrier movable in the direction of the shaft, adjustablescrew means in alignment with the shaft carried by said carrier fordetermining the initial-adjustment of said shaftand for actuating thesame,

the screw thread lever s is transmitted to length, said means 3. In aradio receiver oi the type Provided with one or more permeability tunedcircuits and wherein the tuning means for each such circuit isconstituted by a magnetic core mounted on a shatt and e in the field ofan inductanee coil included for actuating said mean carried by said theextent of linear dismeans for actuating the shaft in the direction ofits comprising a carrier movable second adjustable screw manuallyoperable means for con-v in the tuned circuit, means operable. means fortable'meamand controlling the movement of the pivoted member.

in the direction of the shaft, a first settable means 7 carried by saidcarrier and in alignment with the core shaft for determining the initialadjustment of said shaft and for actuating said shalt. a second settablemeans carried by said carrier for determining the extent of linear dis-1 placement of actuating the the shaft, a pivoted member for carrierthrough said second set- 4. In a radio receiver of the type providedwith one or wherein the tuning athr said able in direction 0! the shaft,a first adjustable screw mean in alignment wlth the shaft carrie by andcarrier for determining the initial adjustment of v the same, secondadjustable screw means car-- ried by said carrier for. determining theextent or lineardisplacement or the shaft, a pivoted member foractuating the carrier through the second adjustable screw means, and

operable means for controlling the movement or the pivoted member. i

Paznmm Herman: GUSDORF.

more permeability tuned circuits and I said shalt and for actuating"

